1. Field of the Invention
The present invention relates to an image forming apparatus and, more particularly, to a configuration of a fixing device which fixes a toner image transferred to a sheet on the sheet by a fixing roller and a pressure roller.
2. Description of the Related Art
In the related art, an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine, which forms an image by an electrophotographic system includes an image forming portion which forms a toner image, a transfer portion which transfers the toner image onto a sheet, and a fixing device which fixes the transferred toner image on the sheet. The fixing device is provided with a fixing roller, a pressure roller, and an entrance guide member, which guides a sheet with an unfixed toner image to a nip portion between the fixing roller and the pressure roller.
In the fixing device of the related art, by the way, when the sheet is jammed at a downstream of the nip portion between the fixing roller and the pressure roller, as illustrated in FIG. 13A, a jammed sheet P will be stopped in the state of being nipped by a fixing roller 1201 and a pressure roller 1203. In this case, a jam recovery operation is performed in such a manner that the jammed sheet P is reversely conveyed upstream in a sheet conveying direction by rotating the fixing roller 1201 in a counterclockwise direction indicated by an arrow.
At this time, however, as illustrated in FIG. 13B, the jammed sheet P sometimes enters between an entrance guide 1205 and the pressure roller 1203 depending on a sheet state. In this case, the entrance guide 1205 has to be detached in order to recover the jammed sheet. In order to prevent the jammed sheet P from entering between the entrance guide 1205 and the pressure roller 1203, a technique of disposing a plate-shaped auxiliary guide member, which varies in a thickness direction of the sheet, on a tip end of the entrance guide 1205 is disclosed in Japanese Patent Laid-Open No. 05-341680.
In the image forming apparatus of the related art including the fixing device, when the auxiliary guide member is disposed on the tip end of the entrance guide, the jammed sheet sometimes abuts the auxiliary guide member, depending on the position of the auxiliary guide member at the time of reversely conveying the jammed sheet. At this time, when the stiffness of the auxiliary guide member is weaker than that of the jammed sheet, the jammed sheet enters the lower side of the entrance guide along with a reverse rotation of the fixing roller, and thus it is difficult to recover the jammed sheet.
The invention has been made in view of such circumstances and is to provide an image forming apparatus capable of easily recovering the jammed sheet which is nipped by the fixing roller and the pressure roller.